Electronic data is commonly stored on discs of various types. Disc drives hold and rotate the disc while positioning a mechanism over the disc to read data from it or write data to it. Some conventional disc drives use a "flying" read/write head, or "flying head", to access data stored magnetically on circular or spiral grooves, or tracks, of the data storage disc. Engaging the flying head in a position to access data is referred to as loading the head. Typically, the flying head is positioned over a track at a certain height to allow data reading or data writing. For example, in magneto-optical (MO) disc drives, data is recorded by positioning a head that includes a magnetic coil in proximity to an MO disc, locally heating the MO disc to lower the coercivity of a layer of magnetic media. When the coercivity of the magnetic media is lowered, the magnetic head applies a magnetic field to reverse the magnetic polarity in the heated area recording data on the MO disc. In such MO disc drives, data is read from the magnetic media of the MO disc by illuminating areas of the MO disc with linearly polarized laser light. The Kerr rotation effect causes the plane of polarization of the illuminating laser beam to be rotated. The direction of rotation depends on the magnetic polarity in the illuminated area of the storage media. When the MO disc is read, the polarization rotation is determined with a pair of optical detectors in a polarization beam splitter to produce an output data signal.
In one prior art method, a flying head is in a loaded position on the MO disc when it is not spinning and no data access operation is taking place. For a data access operation, the MO disc is rotated so that an air bearing forms between the MO disc and the flying head. When the flying head is suspended above the MO disc by the air bearing, the flying head can be moved over the MO disc to an appropriate area to perform a data access operation. This technique is referred to as static loading and unloading or as contact-start-stop because the MO disc must be stationary when the head is loaded or unloaded. This technique has several disadvantages. One disadvantage is that part of the MO disc area must be set aside as a landing zone, which reduces the MO disc area available for data storage. Another disadvantage is that the head can crash into the MO disc if the drive is bumped or dropped, if power is suddenly removed from the drive, or if contaminants are on the disc surface at loading and become trapped under the head. When the head crashes into the MO disc, there is a likelihood of damage to the MO disc, loss of data stored on the MO disc, and even destruction of the drive itself.
Yet another disadvantage of prior art static loading/unloading systems is the necessity of providing a very smooth, very flat, slider surface and media surface on which to carry the magnetic head. Such a slider body is needed in static loading/unloading systems to withstand thousands of contact-start-stop events in the life of the disc drive. In addition, static loading/unloading systems also require lubrication and texturing of the media surface.
Another prior art method, called dynamic loading and unloading, loads and unloads the head while the MO disc is spinning. FIG. 1 is a diagram of a some parts of a prior art disc drive that performs dynamic loading and unloading. Suspension 103 is attached to flying head 109. Suspension 103 is typically manufactured of a material with spring characteristics and has a bend 105 created by forming the material of suspension 103. Bend 105 serves the purpose of providing a spring force and stiffness in the direction perpendicular to the surface of MO disc 107. Some other prior art suspensions may include multiple bends. The angle of bend required to produce the appropriate spring force required in a particular disc drive application must be calculated before forming suspension 103. Because the forming process is imprecise, some trial and error may be required to produce a suspension having the required spring force. Typically, the gram load of the suspension is measured after the suspension if formed.
Flying head 109 is loaded by moving suspension 103 over ramp 101. The surface of ramp 101 over which suspension 103 moves has a slope such that suspension 103 and flying head 109 are moved over MO disc at the proper height for read or write operations. When suspension 103 is advanced toward disc 107, suspension 103 is flexed such that the angle of bend 105 is opened.
FIG. 2 is a side view of suspension 103 and flying head 109 showing bend 105. Mounting plate 111 is attached to suspension 103 and to mounting area 113. Actuator arm 113 is a rigid part of the disc drive assembly. Plane 115 is the plane of an MO disc drive in the disc drive assembly incorporating suspension 103. When head 109 is loaded, suspension 103 is flexed, for example by ramp loading as in FIG. 1, so that the surface of head 109 is approximately parallel to plane 115.
Disadvantages of prior art suspension systems include the time and expense required to form a bend in the suspension and test the suspension to confirm that it has the appropriate spring force.